Bearing apparatus having superhard bearing elements

ABSTRACT

Bearing assemblies and apparatuses are disclosed. Such bearing assemblies may be employed in bearing apparatuses for use in downhole motors of a subterranean drilling system or other mechanical systems. In an embodiment of the present invention, a bearing apparatus includes a first bearing assembly including a first substantially continuous polycrystalline diamond bearing surface defining an annular surface, and a second bearing assembly including a second substantially continuous polycrystalline diamond bearing surface defining an annular surface. The second substantially continuous polycrystalline diamond bearing surface generally opposes the first substantially continuous polycrystalline diamond bearing surface.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of application Ser. No. 13/955,570filed on 31 Jul. 2013, which is a continuation of application Ser. No.13/526,922 filed on 19 Jun. 2012 (now U.S. Pat. No. 8,641,284 issued on4 Feb. 2014), which is a continuation of application Ser. No. 13/014,382filed on 26 Jan. 2011 (now U.S. Pat. No. 8,220,999 issued on 17 Jul.2012), which is a continuation of application Ser. No. 11/974,747 filed15 Oct. 2007 (now U.S. Pat. No. 7,896,551 issued on 1 Mar. 2011), thecontents of each of the foregoing applications are incorporated herein,in their entirety, by reference.

BACKGROUND

Subterranean drilling systems that employ downhole drilling motors arecommonly used for drilling boreholes in the earth for oil and gasexploration. FIG. 1 is a schematic isometric partial cross-sectionalview of a prior art subterranean drilling system 100. The subterraneandrilling system 100 includes a housing 102 enclosing a downhole drillingmotor 104 (i.e., a motor, turbine, or any other device capable ofrotating a shaft) that is operably connected to an output shaft 106. Athrust-bearing apparatus 108 is also operably coupled to the downholedrilling motor 104. A rotary drill bit 112 configured to engage asubterranean formation and drill a borehole is connected to the outputshaft 106. The rotary drill bit 112 is shown as a roller cone bitincluding a plurality of roller cones 114. However, other types ofrotary drill bits, such as so-called “fixed cutter” drill bits are alsocommonly used. As the borehole is drilled, pipe sections may beconnected to the subterranean drilling system 100 to form a drill stringcapable of progressively drilling the borehole to a greater depth withinthe earth.

The thrust-bearing apparatus 108 includes a stator 116 that does notrotate and a rotor 118 that is attached to the output shaft 106 androtates with the output shaft 106. The stator 116 and rotor 118 eachinclude a plurality of bearing elements 120 that may be fabricated frompolycrystalline-diamond compacts that provide diamond bearing surfacesthat bear against each other during use.

In operation, high pressure drilling fluid is circulated through thedrill string and power section (not shown) of the downhole drillingmotor 104, usually prior to the rotary drill bit 112 engaging the bottomof the borehole, to generate torque and rotate the output shaft 106 andthe rotary drill bit 112 attached to the output shaft 106. Unlessrotated from above by the drill rig rotary, the housing 102 of thedownhole drilling motor 104 remains stationary as the output shaft 106rotates the rotary drill bit 112. When the rotary drill bit 112 engagesthe bottom of the borehole, a thrust load is generated, which iscommonly referred to as “on-bottom thrust” that tends to compress thethrust-bearing apparatus 108. The on-bottom thrust is carried, at leastin part, by the thrust-bearing apparatus 108. Fluid flow through thepower section may cause what is commonly referred to as “off-bottomthrust,” which is carried, at least in part, by another thrust-bearingapparatus that is not shown in FIG. 1. The drilling fluid used togenerate the torque for rotating the rotary drill bit 112 exits openingsformed in the rotary drill bit 112 and returns to the surface, carryingcuttings of the subterranean formation through an annular space betweenthe drilled borehole and the subterranean drilling system 100.Typically, a portion of the drilling fluid is diverted by the downholedrilling motor 104 to cool and lubricate both the thrust-bearingapparatus 108 and the other thrust-bearing apparatus.

Both the off-bottom and on-bottom thrust carried by the thrust-bearingapparatuses can be extremely large. Accordingly, the operationallifetime of the thrust-bearing apparatuses often determines the usefullife for the subterranean drilling system 100. For example, despitediamond having a relatively high wear resistance, repetitive contactbetween the bearing elements 120 of the stator 116 and the rotor 118during drilling can cause the bearing elements 120 to wear and,eventually, fail. Moreover, even though the diamond bearing surfaces ofthe bearing elements 120 may have a fairly low coefficient of friction,frictional contact between the diamond bearing surfaces of the stator116 and the rotor 118 can still lower the operational efficiency of thesubterranean drilling system 100 due to frictional losses. Therefore,manufacturers and users of subterranean drilling systems continue toseek bearing apparatuses with improved wear resistance and efficiency.

SUMMARY

Hydrodynamic bearing assemblies and bearing apparatuses are disclosed.Such hydrodynamic bearing assemblies may be employed in bearingapparatuses for use in downhole motors of a subterranean drilling systemor other mechanical systems. In one embodiment of the present invention,a hydrodynamic bearing assembly includes a plurality of bearing elementsdistributed circumferentially about an axis. Each bearing segmentincludes a superhard bearing surface. The plurality of bearing elementsdefines a plurality of seams. Each seam is formed betweencircumferentially-adjacent bearing elements of the plurality of bearingelements.

Further embodiments of the present invention include a hydrodynamicbearing apparatus (e.g., a radial-bearing apparatus and a thrust-bearingapparatus) and a downhole motor that may utilize any of the disclosedhydrodynamic bearing assemblies.

BRIEF DESCRIPTION OF THE DRAWINGS

The drawings illustrate several embodiments of the present invention,wherein like reference numerals refer to like elements or features indifferent views or embodiments shown in the drawings.

FIG. 1 is a schematic isometric partial cross-sectional view of a priorart subterranean drilling system including a thrust-bearing apparatus.

FIG. 2A is an isometric view of a hydrodynamic thrust-bearing assemblyaccording to one embodiment of the present invention.

FIG. 2B is an isometric partial cross-sectional view taken along line2B-2B of the hydrodynamic thrust-bearing assembly shown in FIG. 2A.

FIG. 2C is an isometric view of the support ring shown in FIGS. 2A and2B according to one embodiment of the present invention.

FIG. 2D is an isometric view of two adjacent bearing elements shown inFIGS. 2A and 2B assembled together to form a seam therebetween.

FIG. 2E is a top plan view of the two adjacent bearing elements shown inFIG. 2D.

FIG. 2F is a top plan view of two adjacent bearing elements, with eachbearing segment including substantially planar ends, according toanother embodiment of the present invention.

FIG. 2G is a top plan view of two adjacent bearing elements, with eachbearing segment including curved ends, according to yet anotherembodiment of the present invention.

FIG. 3 is top plan view of a bearing segment comprising ends configuredto limit fluid leakage according to another embodiment of the presentinvention.

FIG. 4A is a top plan view of the two adjacent bearing elements shown inFIGS. 2D and 2E, with a sealant material disposed within the seam,according to another embodiment of the present invention.

FIG. 4B is a cross-sectional view of the two adjacent bearing elementsshown in FIG. 4B taken along line 4B-4B.

FIG. 5A is an isometric view of a thrust-bearing apparatus that mayemploy any of the disclosed hydrodynamic thrust-bearing assembliesaccording to one embodiment of the present invention, with the housingshown in cross-section.

FIG. 5B is an isometric view of the thrust-bearing apparatus shown inFIG. 5A taken along line 5B-5B.

FIG. 5C is an isometric partial cross-sectional view of thethrust-bearing apparatus shown in FIG. 5A taken along line 5B-5B showinga fluid film that develops between the bearing elements of the rotor andstator during certain operational conditions, with the shaft and housingnot shown for clarity.

FIG. 5D is an isometric view of the rotor shown in FIGS. 5A and 5B.

FIG. 5E is a cross-sectional view of a bearing element including aleading section exhibiting a concavely curved geometry according toanother embodiment of the present invention.

FIG. 5F is a cross-sectional view of a bearing element including aleading section geometry exhibiting a convexly curved geometry accordingto a further embodiment of the present invention.

FIG. 5G is a cross-sectional view of a bearing element including aleading section exhibiting a non-planar geometry according to yetanother embodiment of the present invention.

FIG. 6A is an isometric view of a hydrodynamic radial-bearing assemblyaccording to another embodiment of the present invention.

FIG. 6B is an isometric partial cross-sectional view taken along line6B-6B.

FIG. 6C is an isometric view of the support ring shown in FIGS. 6A and6B according to one embodiment of the present invention.

FIG. 6D is an isometric view of one of the bearing elements shown inFIGS. 6A and 6B.

FIG. 7A is an isometric partial cross-sectional view of a radial-bearingapparatus that may utilize any of the disclosed hydrodynamicradial-bearing assemblies according to one embodiment of the presentinvention.

FIG. 7B is an exploded isometric view of the radial-bearing apparatusshown in FIG. 7A.

FIG. 8 is a schematic isometric partial cross-sectional view of asubterranean drilling system including a thrust-bearing apparatusutilizing any of the previously described bearing assemblies accordingto various embodiments of the present invention.

DETAILED DESCRIPTION

Embodiments of the present invention relate to a hydrodynamic bearingassembly (e.g., a rotor or stator of a thrust-bearing apparatus)including a plurality of bearing elements assembled together to form asubstantially continuous bearing element. The disclosed hydrodynamicbearing assemblies may be employed in bearing apparatuses for use in adownhole motor of a subterranean drilling system and other mechanicalsystems.

FIGS. 2A and 2B are isometric and isometric partial cross-sectionalviews, respectively, of a hydrodynamic thrust-bearing assembly 200according to one embodiment of the present invention. The hydrodynamicthrust-bearing assembly 200 includes a support ring 202 that carries aplurality of circumferentially-adjacent, arcuately-shaped bearingelements 204. The bearing elements 204 are distributed about a thrustaxis 205 along which a thrust force may be generally directed duringuse. Each bearing segment 204 is located circumferentially adjacent toanother bearing segment 204, with a seam 206 formed therebetween. Thebearing elements 204 collectively form a substantially continuousbearing element. The support ring 202 may include an inner, peripheralsurface 207 defining an aperture 209 generally centered about the thrustaxis 205. The aperture 209 may receive a motor shaft (e.g., a downholedrilling motor shaft).

As shown in FIG. 2B, each bearing segment 204 may be a superhard compact(e.g., a polycrystalline diamond compact (“PDC”)) that includes asuperhard table 208 of superhard material (e.g., polycrystallinediamond) bonded to a substrate 210 (e.g., a cobalt-cemented tungstencarbide substrate). Each superhard table 208 includes a bearing surface212. The bearing surfaces 212 of the superhard tables 208 collectivelyform a substantially continuous bearing surface. The term “superhard,”as used herein, means a material having a hardness at least equal to ahardness of tungsten carbide. Any superhard material may be used, suchas silicon carbide, a diamond-silicon carbide composite, polycrystallinecubic boron nitride, polycrystalline cubic boron nitride andpolycrystalline diamond, silicon carbide and polycrystalline boronnitride mixed with polycrystalline diamond, or any other suitablesuperhard material or mixture of superhard materials. However, incertain embodiments of the present invention, the superhard tables 208may be omitted, and each bearing segment 204 may be made from asuperhard material, such as cemented tungsten carbide.

FIG. 2C is an isometric view of the support ring 202 that illustratesthe configuration thereof in more detail. The support ring 202 includesan annular slot 214 defined by a circumferentially extending outer wall216, a circumferentially extending inner wall 218, and a base 220. Thebearing elements 204 (FIGS. 2A and 2B) may be assembled within theannular slot 214 and secured to the support ring 202 within the annularslot 214 by brazing the bearing elements 204 (FIGS. 2A and 2B) to thesupport ring 202, press-fitting the bearing elements 204 (FIGS. 2A and2B) to the support ring 202 and/or with or against each other, attachingeach of the bearing elements 204 (FIGS. 2A and 2B) to the support ring202 with a fastener, or another suitable technique. It is noted that thesupport ring 202 merely represents one embodiment for a support ring andother configurations may be used. For example, according to anotherembodiment of the present invention, a support ring may lack an annularslot.

FIGS. 2D and 2E are isometric and plan views, respectively, that showthe structure of the bearing elements 204 and the manner in which thebearing elements 204 may be assembled together. Each bearing segment 204includes a first end region 218 and a second end region 220, with one ofthe bearing surfaces 212 extending therebetween. Each first end region218 and second end region 220 may be configured to limit fluid frombeing able to leak through the seams 206 formed between adjacent bearingelements 204. For example, the second end region 220 of one bearingsegment 204 may be configured to correspond with and, in someembodiments, may mesh with the first end region 218 of an adjacentbearing segment 204. In the illustrated embodiment, each first endregion 218 and second end region 220 of the bearing elements 204 isconfigured with a serrated geometry. Such a configuration may provide atortuous path to limit fluid leakage radially through the seams 206.Depending upon the tolerances of the bearing elements 204, all or aportion of the seams 206 may comprise a relatively small gap 222. Forexample, the gap 222 may exhibit a width of about 0.00020 inches (0.0051mm) to about 0.100 inches (2.54 mm), and more particularly about 0.00020inches (0.0051 mm) to about 0.020 inches (0.051 mm). In anotherembodiment of the present invention shown in FIG. 2F, a first end region218′ and a second end region 220′ of each bearing segment 204′ may besubstantially planar and may abut with each other when assembled. In yeta further embodiment of the present invention shown in FIG. 2G, a firstend region 218″ and a second end region 220″ of each bearing segment204″ may exhibit curved surfaces configured to mate with each other whenassembled.

In other embodiments of the present invention, each first end region 218and second end region 220 may exhibit another, selected non-planarconfiguration that departs from the illustrated embodiment shown inFIGS. 2D and 2E. For example, FIG. 3 is a top plan view that shows abearing segment 300 according to another embodiment of the presentinvention. The bearing segment 300 includes a superhard table 302 bondedto a substrate (not shown) including a first end region 304, a secondend region 306, and a bearing surface 308 of the superhard table 302extending between the first end region 304 and second end region 306.The first end region 304 comprises rectangular-shaped slots 310 andrectangular-shaped ridges 312 and the second end region 306 alsoincludes rectangular-shaped slots 314 and rectangular-shaped ridges 316to enable at least partial interlocking of a first end region 304 of onebearing segment 300 with a second end region 306 of another,circumferentially-adjacent bearing segment 300.

As discussed above, each bearing segment 204 is positionedcircumferentially adjacent to another bearing segment 204, with one ofthe seams 206 formed therebetween. If present, the gaps 222 locatedbetween adjacent bearing elements 204 may be filled with a sealantmaterial to help further prevent leakage of fluid through the seams 206(e.g., radially outwardly). For example, FIGS. 4A and 4B are isometricand cross-sectional views, respectively, that show another embodiment ofthe present invention in which the gaps 222 shown in FIG. 2E may besubstantially filed with a sealant material 400. For example, thesealant material 400 may comprise a ceramic material, a metallicmaterial, a polymeric material, or another suitable material. In oneembodiment of the present invention, the sealant material 400 mayexhibit abrasion and/or erosion resistance to commonly used drillingfluids (also known as drilling mud). For example, the sealant material400 may comprise chemically-vapor-deposited (“CVD”) diamond or achemically-vapor-deposited carbide material (e.g., binderless tungstencarbide). Specifically, one example of a commercially available CVDbinderless tungsten carbide material (currently marketed under thetrademark HARDIDE®) is currently available from Hardide Layers Inc. ofHouston, Tex. In other embodiments, a binderless tungsten carbidematerial may be formed by physical vapor deposition (“PVD”), variants ofPVD, high-velocity oxygen fuel (“HVOF”) thermal spray processes, or anyother suitable process, without limitation. In other embodiments of thepresent invention, the braze alloy used to braze the bearing elements204 to the support ring 202 may infiltrate the seams 206 andsubstantially fill the gaps 222. For example, suitable abrasionresistant braze alloys include, but are not limited to, silver-copperbased braze alloys commercially available from Handy & Harmon of CanadaLimited known as braze 505 and braze 516 may be employed. In anotherembodiment of the present invention, the sealant material 400 may alsocomprise a hardfacing material (e.g., a nickel or cobalt alloy) appliedat least within the gaps 222 by thermal spraying. In yet a furtherembodiment of the present invention, the sealant material 400 maycomprise polyurethane or another suitable polymeric material.

In another embodiment of the present invention, a substantiallycontinuous superhard bearing surface may be formed by depositing a layerof diamond onto a generally planar surface of a support ring. Forexample, the layer of diamond may be deposited using chemical vapordeposition.

Any of the above-described hydrodynamic thrust-bearing assembliesembodiments may be employed in a hydrodynamic thrust-bearing apparatus.FIGS. 5A and 5B are isometric partial cross-sectional views of ahydrodynamic thrust-bearing apparatus 500 according to one embodiment ofthe present invention. The hydrodynamic thrust-bearing apparatus 500 mayinclude a stator 502 configured as any of the previously describedembodiments of hydrodynamic thrust-bearing assemblies. The stator 502includes a plurality of circumferentially-adjacent bearing elements 504(e.g., a plurality of superhard compacts), each of which includes abearing surface 505 and may exhibit, for example, the configuration ofthe bearing segment 204. The bearing elements 504 may be mounted orotherwise attached to a support ring 506. The hydrodynamicthrust-bearing apparatus 500 further includes a rotor 508. The rotor 508includes a support ring 512 and a plurality of bearing elements 514(e.g., a plurality of superhard compacts) mounted or otherwise attachedto the support ring 512, with each of the bearing elements 514 having abearing surface 515. The terms “rotor” and “stator” refer to rotatingand stationary components of the thrust-bearing apparatus 500,respectively. As shown in FIG. 5B, a shaft 510 may be coupled to thesupport ring 512 and operably coupled to an apparatus capable ofrotating the shaft section 510 in a direction R (or in an oppositedirection), such as a downhole motor. For example, the shaft 510 mayextend through and may be secured to the support ring 512 of the rotor508 by press-fitting or threadly coupling the shaft 510 to the supportring 512 or another suitable technique. A housing 511 may be secured tothe support ring 506 of the stator 502 by, for example, press-fitting orthreadly coupling the housing 511 to the support ring 506 and may extendcircumferentially about the shaft 510 and the rotor 508.

The operation of the hydrodynamic thrust-bearing apparatus 500 isdiscussed in more detail with reference to FIGS. 5B and 5C. FIG. 5C isan isometric partial cross-sectional view in which the shaft 510 andhousing 511 are not shown for clarity. As shown in FIG. 5B, inoperation, drilling fluid or mud 516 may be pumped between the shaft 510and the housing 511, and between the bearing elements 514 of the rotor508. As shown in FIG. 5C, rotation of the rotor 508 at a sufficientrotational speed sweeps the drilling fluid onto bearing surfaces 505 ofthe stator 502 and allows a fluid film 517 to develop between thebearing surfaces 505 of the stator 502 and the bearing surfaces 515 ofthe rotor 508. Because the stator 502 includes a plurality of theclosely-spaced bearing elements 504, the fluid film 517 may developunder certain operational conditions in which the rotational speed ofthe rotor 508 is sufficiently great and the thrust load is sufficientlylow. Under certain operational conditions, the pressure of the fluidfilm 517 is sufficient to prevent contact between the bearing surfaces505 of the stator 502 and the bearing surfaces 515 of the rotor 508 and,thus, substantially reduce wear of the bearing elements 504 and bearingelements 514. When the thrust loads exceed a certain value and/or therotational speed of the rotor 508 is reduced, the pressure of the fluidfilm 517 is not sufficient to prevent the bearing surfaces 505 of thestator 502 and the bearing surfaces 515 of the rotor 508 from contactingeach other. Under such operational conditions, the hydrodynamicthrust-bearing apparatus 500 is not operated as a hydrodynamic bearing.Thus, under certain operational conditions, the hydrodynamicthrust-bearing apparatus 500 may be operated as a hydrodynamicthrust-bearing apparatus and under other conditions the hydrodynamicthrust-bearing apparatus 500 may be operated so that the bearingsurfaces 505 and bearing surfaces 515 contact each other during use or apartially developed fluid film is present between the bearing surfaces505 and bearing surfaces 515. However, the bearing elements 504 andbearing elements 514 comprising superhard materials are sufficientlywear-resistant to accommodate repetitive contact with each other, suchas during start-up and shut-down of a subterranean drilling systememploying the hydrodynamic thrust-bearing apparatus 500 or otheroperational conditions not favorable for forming the fluid film 517.

It is noted that in certain embodiments of the present invention, therotor may be configured as any of the previously described embodimentsof hydrodynamic thrust-bearing assemblies instead of the stator.

FIG. 5D is a top isometric view of the rotor 508 that illustrates theconfiguration of the bearing elements 514 thereof in more detail. Thebearing surface 515 of each bearing elements 514 may include a loadbearing section 518 and a leading section 520 that is configured topromote formation of the fluid film 517 (FIG. 5C). For example, eachbearing element 514 may include a superhard table bonded to a substrate,with the load bearing section 518 and the leading section 520 formed inthe superhard table. The leading section 520 may slope at an anglerelative to the load bearing section 518. The leading section 518 may beconfigured to promote sweeping the drilling fluid 516 (FIGS. 5B and 5C)between the bearing surfaces 505 (FIG. 5C) of the stator 502 (FIG. 5C)and, consequently, formation of the fluid film 517 shown in FIG. 5Cwhile the rotor 508 is rotated. When operated under conditions thatallow for formation of the fluid film 517, the load bearing section 518and the bearing surfaces 505 of the stator 502 (FIG. 5C) may not contacteach other due to the pressure of the fluid film 517 (FIG. 5C).

In other embodiments of the present invention, each bearing element ofthe rotor 508 may include a leading section that exhibits a non-planargeometry. For example, FIG. 5E is a cross-sectional view of a bearingelement 514′ according to another embodiment of the present invention.The bearing element 514′ includes a load bearing section 518′, with aleading section 520′ that may arcuately approach the load bearingsection 518 and exhibit a concave curvature. FIG. 5F is across-sectional view of a bearing element 514″ according to anotherembodiment of the present invention. The bearing element 514″ includes aload bearing section 518″, with a leading section 520″ that mayarcuately approach the load bearing section 518 and exhibit a convexcurvature. FIG. 5G is a cross-sectional view of a bearing element 514′″according to another embodiment of the present invention. The bearingelement 514′″ includes a load bearing section 518′″, with a leadingsection 520′″ comprising a first section 522 that may be substantiallyparallel to the load bearing section 518′″ and a second section 524 thatslopes at an angle from the load bearing section 518′″ and may besubstantially planar. In yet another embodiment of the presentinvention, the leading section 520 may include a slot or recess formedtherein configured to promote forming the fluid film 517 (FIG. 5C)between the bearing elements 514 of the rotor 508 and the bearingelements 504 of the stator 502 that may be as a result of a beneficialradial pressure gradient over the bearing elements 514. In otherembodiments of the present invention, the bearing elements 514 may beconventional in construction, without the leading edge sections 220.

The concepts used in the thrust-bearing assemblies and apparatusesdescribed above may also be employed in radial-bearing assemblies andapparatuses. FIGS. 6A and 6B are isometric and isometric partialcross-sectional views, respectively, illustrating a radial-bearingassembly 600 according to one embodiment of the present invention. Theradial-bearing assembly 600 includes a support ring 602 extending aboutan axis 604. The support ring 602 includes an interior surface 606defining an opening 608 that is capable of receiving, for example, ashaft of a motor from a downhole motor assembly or other apparatus. Aplurality of bearing elements 610 are distributed circumferentiallyabout the axis 604. Each bearing segment 610 comprises a superhard table612 including a convexly-curved bearing surface 614. Each superhardtable 612 may be bonded to a corresponding substrate 616. (FIGS. 6B and6D). Each bearing surface 614 may be convexly curved to lie on animaginary cylindrical surface. The superhard tables 612 and substrates616 may be fabricated from the same materials described above for thebearing elements 204 shown in FIGS. 2A and 2B.

With continued reference to FIGS. 6A and 6B, a seam 618 is formedbetween circumferentially-adjacent bearing elements 610. As with thethrust-bearing assembly 200 described above, if desired, any of thepreviously described sealant materials may be disposed within a gap (notshown) that may be formed between adjacent bearing elements 610 to helpfurther prevent fluid leakage through the seams 618.

FIG. 6C is an isometric view of the support ring 602 that shows theconfiguration thereof in more detail. The support ring 602 includes acircumferentially extending recess 620 partially defined by generallyplanar surfaces 622 that intersect each other an angle greater than zerodegrees. The bearing elements 610 may be secured within the slot 620 bybrazing, press-fitting, using fasteners, or another suitable technique.

FIG. 6D is an isometric view of one of the bearing elements 610 thatshows the structure thereof in more detail, which may be representativeof all of the bearing elements 610 shown in FIGS. 6A and 6B. As shownand discussed above, the bearing segment 610 includes a superhard table612 bonded to the substrate 616. As with the bearing elements 204, thebearing segment 610 includes a first end region 624 and a second endregion 626, with the bearing surface 614 extending therebetween. Thefirst end region 624 and second end region 624 may exhibit any of thepreviously described geometries, such as a serrated geometry illustratedin FIGS. 6A through 6D or the end geometries shown in FIGS. 2F, 2G, and3 to enable mating adjacent bearing elements together and limit fluidleakage through seams between adjacent bearing elements.

FIGS. 7A and 7B are isometric partial cross-sectional and explodedisometric views, respectively, of a radial-bearing apparatus 700according to yet another embodiment of the present invention. Theradial-bearing apparatus 700 includes an inner race 702 (i.e., a stator)that may be configured as the radial-bearing assembly 600 shown in FIG.6A. The inner race 702 defines an opening 703 and includes a pluralityof circumferentially-adjacent bearing elements 704 (e.g., a plurality ofsuperhard compacts), each of which includes a convexly-curved bearingsurface 706. The radial-bearing apparatus 700 further includes an outerrace 708 (i.e., a rotor) that extends about and receives the inner race702. The outer race 708 includes a plurality of circumferentially-spacedbearing elements 710 (e.g., a plurality of superhard compacts), each ofwhich includes a concavely-curved bearing surface. The terms “rotor” and“stator” refer to rotating and stationary components of theradial-bearing apparatus 700, respectively. Thus, if the outer race 708is configured to remain stationary, the outer race 708 can be referredto as the stator and the inner race 702 can be referred to as the rotor.

Each concavely-curved bearing surface of a corresponding bearing element710 may include a load bearing section 714 and leading sections 716.Each leading section 716 may be slanted at an angle relative to the loadbearing section 714 in a radial outward direction or may exhibit aleading section geometry similar to the leading sections shown in FIGS.5E-5G. For example, each bearing element 710 may be configured as asuperhard compact including a superhard table bonded to a substrate,with the load bearing section 714 and leading section 716 formed in thesuperhard table. The leading sections 716 help sweep lubricant onto thebearing surfaces 706 of the stator 702 to form a fluid film in a mannersimilar to the leading sections 520 of the bearing elements 514 shown inFIG. 5D. It is noted, that in other embodiments of the presentinvention, the bearing elements 710 may also be conventional inconstruction, without the slanted leading sections 716. A shaft orspindle (not shown) may extend through the opening 703 and may besecured to the stator 702 by press-fitting the shaft or spindle to thestator 702, threadly coupling the shaft or spindle to the stator 702, oranother suitable technique. A housing (not shown) may also be secured tothe rotor 704 using similar techniques.

The radial-bearing apparatus 700 may be employed in a variety ofmechanical applications. For example, so-called “roller cone” rotarydrill bits may benefit from a radial-bearing apparatus disclosed herein.More specifically, the inner race 702 may be mounted or affixed to aspindle of a roller cone and the outer race 708 may be affixed to aninner bore formed within a cone and that such an outer race 708 andinner race 702 may be assembled to form a radial-bearing apparatus.

It is noted that the inner race 702 of the radial-bearing assembly 700is shown with a plurality of circumferentially-adjacent bearing elementsassembled together to form a substantially continuous bearing element.However, in other embodiments of the present invention, an outer race ofa radial-bearing apparatus may include a plurality ofcircumferentially-adjacent bearing elements assembled together that forma substantially continuous bearing element. In such an embodiment, aninner race of the radial-bearing apparatus may include a plurality ofcircumferentially-adjacent bearing elements, each of which may include aleading section, as previously described, configured to promote sweepinglubricant onto the substantially continuous bearing element of the outerrace during operation.

In operation, rotation of the shaft sections (not shown) secured to therotor 708 effects rotation of the rotor 708 relative to the stator 702.Drilling fluid or other lubricant may be pumped between the bearingsurfaces 712 of the rotor 708 and the bearing surfaces 706 of the stator702. When the rotor 704 rotates, the leading edge sections 716 of thebearing elements 710 may sweep lubricant (e.g., drilling fluid or otherlubricant) onto the bearing surfaces 706 of the stator 702. Aspreviously described with respect to the thrust-bearing apparatus 500,at sufficient rotational speeds for the rotor 708, a fluid film maydevelop between the bearing surface 712 of the bearing elements 710 andthe bearing surfaces 706 of the bearing elements 704 having sufficientpressure to maintain the bearing surfaces 712 and the bearing surfaces706 apart from each other. Accordingly, wear on the bearing elements 710and bearing elements 702 may be reduced compared to when direct contactbetween the bearing elements 710 and bearing elements 702 occurs.

Any of the embodiments for bearing apparatuses discussed above may beused in a subterranean drilling system. FIG. 8 is a schematic isometricpartial cross-sectional view of a subterranean drilling system 800according to one embodiment of the present invention that uses ahydrodynamic thrust-bearing apparatus. The subterranean drilling system800 includes a housing 802 enclosing a downhole drilling motor 804(i.e., a motor, turbine, or any other device capable of rotating anoutput shaft) that is operably connected to an output shaft 806. Ahydrodynamic thrust-bearing apparatus 808 is operably coupled to thedownhole drilling motor 804. The hydrodynamic thrust-bearing apparatus808 may be configured as any of the previously described hydrodynamicthrust-bearing apparatus embodiments. A rotary drill bit 812 configuredto engage a subterranean formation and drill a borehole is connected tothe output shaft 806. The rotary drill bit 812 is shown as a roller conebit including a plurality of roller cones 814. However, otherembodiments of the present invention may utilize different types ofrotary drill bits, such as so-called “fixed cutter” drill bits. As theborehole is drilled, pipe sections may be connected to the subterraneandrilling system 800 to form a drill string capable of progressivelydrilling the borehole to a greater depth within the earth.

The thrust-bearing apparatus 808 includes a stator 816 that does notrotate and a rotor 818 that is attached to the output shaft 106 androtates with the output shaft 806. The stator 816 may include aplurality of circumferentially-adjacent bearing elements 820 assembledtogether to form a substantially continuous bearing element, aspreviously described such as in the hydrodynamic thrust-bearing assembly200 shown in FIG. 2A. The rotor 818 may include a plurality of bearingelements (not shown) such as shown in the rotor 508 of FIG. 5D.

In operation, drilling fluid may be circulated through the downholedrilling motor 804 to generate torque and effect rotation of the outputshaft 806 and the rotary drill bit 812 attached thereto so that aborehole may be drilled. A portion of the drilling fluid is also used tolubricate opposing bearing surfaces of the stator 816 and rotor 818.When the rotor 818 is rotated at a sufficient rotational speed, thedrilling fluid is swept onto the bearing surfaces of the stator 816 anda fluid film having sufficient pressure may develop that maintains thebearing surfaces of the stator 816 and the bearing surfaces of the rotor818 apart, as previously discussed.

Although the bearing assemblies and apparatuses described above havebeen discussed in the context of subterranean drilling systems andapplications, in other embodiments of the present invention, the bearingassemblies and apparatuses disclosed herein are not limited to such useand may be used for many different applications, if desired, withoutlimitation. Thus, such bearing assemblies and apparatuses are notlimited for use with subterranean drilling systems and may be used withvarious other mechanical systems, without limitation.

Although the present invention has been disclosed and described by wayof some embodiments, it is apparent to those skilled in the art thatseveral modifications to the described embodiments, as well as otherembodiments of the present invention are possible without departing fromthe spirit and scope of the present invention. Additionally, the words“including” and “having,” as used herein, including the claims, shallhave the same meaning as the word “comprising.”

1. A bearing apparatus, comprising: a first bearing assembly including afirst support ring and a plurality of polycrystalline diamond bearingelements brazed to the first support ring, the plurality ofpolycrystalline diamond bearing elements circumferentially-spaced fromeach other; and a second bearing assembly including a second supportring and a substantially continuous polycrystalline diamond bearingelement brazed to the second support ring, the substantially continuouspolycrystalline diamond bearing element defining a substantiallycontinuous polycrystalline diamond bearing surface, the substantiallycontinuous polycrystalline diamond bearing surface generally opposingthe plurality of polycrystalline diamond bearing elements of the firstbearing assembly.
 2. The bearing apparatus of claim 1 wherein thesubstantially continuous polycrystalline diamond bearing elementincludes a plurality of second polycrystalline diamond bearing elementsdefining the substantially continuous polycrystalline diamond bearingsurface, the plurality of second polycrystalline diamond bearingelements defining respective gaps between circumferentially adjacentsecond polycrystalline diamond bearing elements of the plurality ofsecond polycrystalline diamond bearing elements.
 3. The bearingapparatus of claim 2 wherein at least some of the gaps are about 0.0051mm to about 2.54 mm.
 4. The bearing apparatus of claim 3 wherein the atleast some of the gaps are about 0.0051 mm to about 0.051 mm.
 5. Thebearing apparatus of claim 2 wherein each of the plurality of secondpolycrystalline diamond bearing elements includes at least one sidesurface that exhibits a selected non-planar geometry.
 6. The bearingapparatus of claim 5 wherein the selected non-planar geometry exhibits aserrated geometry.
 7. The bearing apparatus of claim 5 wherein theselected non-planar geometry is curved.
 8. The bearing apparatus ofclaim 8 wherein the gaps are at least partially filled with braze alloy.9. The bearing apparatus of claim 2 wherein each of the plurality ofsecond polycrystalline diamond bearing elements includes a substrate anda polycrystalline diamond table bonded to the substrate.
 10. The bearingapparatus of claim 1 wherein the substantially continuouspolycrystalline diamond bearing surface extends circumferentially abouta thrust axis.
 11. The bearing apparatus of claim 1 wherein thesubstantially continuous polycrystalline diamond bearing surface extendscircumferentially about a rotation axis.
 12. A bearing apparatus,comprising: a first bearing assembly including a first support ring anda plurality of circumferentially-spaced superhard bearing elementsbrazed to the first support ring, each of the plurality ofcircumferentially-spaced superhard bearing elements includes a firstsuperhard bearing surface; and a second bearing assembly including: asecond support ring; and a plurality of superhard bearing elementsdistributed circumferentially about an axis and brazed to the secondsupport ring with a braze alloy, each of the second plurality ofsuperhard bearing elements extending beyond the second support ring,each of the plurality of superhard bearing elements including asuperhard bearing surface and at least one side surface, the superhardbearing surfaces of the second bearing assembly generally opposing thefirst superhard bearing surfaces of the first bearing assembly, eachgenerally opposing pair of the at least one side surfaces defining a gaptherebetween that is at least partially filled with the braze alloywhich spans between the generally opposing pair of the at least one sidesurfaces, at least some of the gaps being about 0.0051 mm to about 2.54mm.
 13. The bearing apparatus of claim 12 wherein the at least some ofthe gaps are about 0.0051 mm to about 0.051 mm.
 14. The bearingapparatus of claim 12 wherein the at least one side surface issubstantially planar.
 15. The bearing apparatus of claim 12 wherein theat least one side surface exhibits a selected non-planar geometry. 16.The bearing apparatus of claim 15 wherein the selected non-planargeometry exhibits a serrated geometry.
 17. The bearing apparatus ofclaim 15 wherein the selected non-planar geometry is curved.
 18. Thebearing apparatus of claim 12 wherein each of the plurality of superhardbearing elements at least partially receives a circumferentiallyadjacent one of the plurality of superhard bearing elements.
 19. Athrust-bearing apparatus, comprising: a first bearing assembly includinga first support ring and a plurality of circumferentially-spacedpolycrystalline diamond bearing elements brazed to the first supportring, each of the plurality of circumferentially-spaced polycrystallinediamond bearing elements includes a first polycrystalline diamondbearing surface; and a second bearing assembly including: a secondsupport ring defining a slot; and a plurality of polycrystalline diamondbearing elements received by the slot of the second support ring andbrazed to the second support ring with a braze alloy, the plurality ofpolycrystalline diamond bearing distributed circumferentially about athrust axis, each of the plurality of polycrystalline diamond bearingelements extending beyond the second support ring, each of the pluralityof polycrystalline diamond bearing elements including a polycrystallinediamond bearing surface and at least one side surface, thepolycrystalline diamond bearing surfaces of the second bearing assemblygenerally opposing the first polycrystalline diamond bearing surfaces ofthe first bearing assembly, each of the plurality of polycrystallinediamond bearing elements at least partially receives a circumferentiallyadjacent one of the plurality of polycrystalline diamond bearingelements.
 20. The thrust-bearing apparatus of claim 19 wherein eachgenerally opposing pair of the at least one side surfaces defining a gaptherebetween that is at least partially filled with the braze alloy, atleast some of the gaps are about 0.0051 mm to about 2.54 mm.